OSX FSEvents support

Needs work to deal with directory renames better; otherwise seems to
basically work.

Utility/DirWatcher.hs

@@ -1,7 +1,8 @@
 {- generic directory watching interface
  -
- - Uses either inotify or kqueue to watch a directory (and subdirectories)
- - for changes, and runs hooks for different sorts of events as they occur.
+ - Uses inotify, or kqueue, or fsevents to watch a directory
+ - (and subdirectories) for changes, and runs hooks for different
+ - sorts of events as they occur.
  -
  - Copyright 2012 Joey Hess <joey@kitenet.net>
  -
@@ -22,11 +23,15 @@ import qualified System.INotify as INotify
 import qualified Utility.Kqueue as Kqueue
 import Control.Concurrent
 #endif
+#if WITH_FSEVENTS
+import qualified Utility.FSEvents as FSEvents
+import qualified System.OSX.FSEvents as FSEvents
+#endif
 
 type Pruner = FilePath -> Bool
 
 canWatch :: Bool
-#if (WITH_INOTIFY || WITH_KQUEUE)
+#if (WITH_INOTIFY || WITH_KQUEUE || WITH_FSEVENTS)
 canWatch = True
 #else
 #if defined linux_HOST_OS
@@ -42,7 +47,7 @@ canWatch = False
  - OTOH, with kqueue, often only one event is received, indicating the most
  - recent state of the file. -}
 eventsCoalesce :: Bool
-#if WITH_INOTIFY
+#if (WITH_INOTIFY || WITH_FSEVENTS)
 eventsCoalesce = False
 #else
 #if WITH_KQUEUE
@@ -55,12 +60,15 @@ eventsCoalesce = undefined
 {- With inotify, file closing is tracked to some extent, so an add event
  - will always be received for a file once its writer closes it, and
  - (typically) not before. This may mean multiple add events for the same file.
+ - 
+ - fsevents behaves similarly, although different event types are used for
+ - creating and modification of the file.
  -
  - OTOH, with kqueue, add events will often be received while a file is
  - still being written to, and then no add event will be received once the
  - writer closes it. -}
 closingTracked :: Bool
-#if WITH_INOTIFY
+#if (WITH_INOTIFY || WITH_FSEVENTS)
 closingTracked = True
 #else
 #if WITH_KQUEUE
@@ -71,9 +79,11 @@ closingTracked = undefined
 #endif
 
 {- With inotify, modifications to existing files can be tracked.
- - Kqueue does not support this. -}
+ - Kqueue does not support this.
+ - Fsevents generates events when an existing file is reopened and rewritten,
+ - but not necessarily when it's opened once and modified repeatedly. -}
 modifyTracked :: Bool
-#if WITH_INOTIFY
+#if (WITH_INOTIFY || WITH_FSEVENTS)
 modifyTracked = True
 #else
 #if WITH_KQUEUE
@@ -83,9 +93,9 @@ modifyTracked = undefined
 #endif
 #endif
 
-{- Starts a watcher thread. The runStartup action is passed a scanner action
+{- Starts a watcher thread. The runstartup action is passed a scanner action
  - to run, that will return once the initial directory scan is complete.
- - Once runStartup returns, the watcher thread continues running,
+ - Once runstartup returns, the watcher thread continues running,
  - and processing events. Returns a DirWatcherHandle that can be used
  - to shutdown later. -}
 #if WITH_INOTIFY
@@ -103,11 +113,18 @@ watchDir dir prune hooks runstartup = do
 	kq <- runstartup $ Kqueue.initKqueue dir prune
 	forkIO $ Kqueue.runHooks kq hooks
 #else
+#if WITH_FSEVENTS
+type DirWatcherHandle = FSEvents.EventStream
+watchDir :: FilePath -> Pruner -> WatchHooks -> (IO FSEvents.EventStream -> IO FSEvents.EventStream) -> IO DirWatcherHandle
+watchDir dir prune hooks runstartup =
+	runstartup $ FSEvents.watchDir dir prune hooks
+#else
 type DirWatcherHandle = ()
 watchDir :: FilePath -> Pruner -> WatchHooks -> (IO () -> IO ()) -> IO DirWatcherHandle
 watchDir = undefined
 #endif
 #endif
+#endif
 
 #if WITH_INOTIFY
 stopWatchDir :: DirWatcherHandle -> IO ()
@@ -117,7 +134,12 @@ stopWatchDir = INotify.killINotify
 stopWatchDir :: DirWatcherHandle -> IO ()
 stopWatchDir = killThread
 #else
+#if WITH_FSEVENTS
+stopWatchDir :: DirWatcherHandle -> IO ()
+stopWatchDir = FSEvents.eventStreamDestroy
+#else
 stopWatchDir :: DirWatcherHandle -> IO ()
 stopWatchDir = undefined
 #endif
 #endif
+#endif